Department of Biomedical Engineering, University of Massachusetts Amherst, Amherst, Massachusetts, United States of America.
Institute of Applied Life Sciences, University of Massachusetts Amherst, Amherst, Massachusetts, United States of America.
PLoS Comput Biol. 2023 Apr 12;19(4):e1011012. doi: 10.1371/journal.pcbi.1011012. eCollection 2023 Apr.
Transcranial direct current stimulation (tDCS) can noninvasively modulate behavior, cognition, and physiologic brain functions depending on polarity and dose of stimulation as well as montage of electrodes. Concurrent tDCS-fMRI presents a novel way to explore the parameter space of non-invasive brain stimulation and to inform the experimenter as well as the participant if a targeted brain region or a network of spatially separate brain regions has been engaged and modulated. We compared a multi-electrode (ME) with a single electrode (SE) montage and both active conditions with a no-stimulation (NS) control condition to assess the engagement of a brain network and the ability of different electrode montages to modulate network activity. The multi-electrode montage targeted nodal regions of the right Arcuate Fasciculus Network (AFN) with anodal electrodes placed over the skull position of the posterior superior temporal/middle temporal gyrus (STG/MTG), supramarginal gyrus (SMG), posterior inferior frontal gyrus (IFG) and a return cathodal electrode over the left supraorbital region. In comparison, the single electrode montage used only one anodal electrode over a nodal brain region of the AFN, but varied the location between STG/MTG, SMG, and posterior IFG for different participants. Whole-brain rs-fMRI was obtained approximately every three seconds. The tDCS-stimulator was turned on at 3 minutes after the scanning started. A 4D rs-fMRI data set was converted to dynamic functional connectivity (DFC) matrices using a set of ROI pairs belonging to the AFN as well as other unrelated brain networks. In this study, we evaluated the performance of five algorithms to classify the DFC matrices from the three conditions (ME, SE, NS) into three different categories. The highest accuracy of 0.92 was obtained for the classification of the ME condition using the K Nearest Neighbor (KNN) algorithm. In other words, applying the classification algorithm allowed us to identify the engagement of the AFN and the ME condition was the best montage to achieve such an engagement. The top 5 ROI pairs that made a major contribution to the classification of participant's rs-fMRI data were identified using model performance parameters; ROI pairs were mainly located within the right AFN. This proof-of-concept study using a classification algorithm approach can be expanded to create a near real-time feedback system at a participant level to detect the engagement and modulation of a brain network that spans multiple brain lobes.
经颅直流电刺激(tDCS)可以非侵入性地调节行为、认知和生理脑功能,具体取决于刺激的极性和剂量以及电极的排列方式。同时进行 tDCS-fMRI 为探索非侵入性脑刺激的参数空间提供了一种新方法,并为实验者和参与者提供信息,以确定目标脑区或空间分离的脑区网络是否被激活和调节。我们比较了多电极(ME)和单电极(SE)两种排列方式,以及两种激活状态与无刺激(NS)对照状态,以评估脑网络的激活情况以及不同电极排列方式调节网络活动的能力。多电极排列方式以阳极电极置于后上颞叶/中颞叶(STG/MTG)、缘上回(SMG)、后额下回(IFG)的颅骨位置,阴极返回电极置于左侧眶上区域,以靶向右侧弓状束网络(AFN)的节点区域。相比之下,单电极排列方式仅在 AFN 的一个节点脑区使用一个阳极电极,但针对不同的参与者,其位置在 STG/MTG、SMG 和后 IFG 之间变化。全脑 rs-fMRI 大约每三秒钟采集一次。tDCS 刺激器在扫描开始后 3 分钟打开。使用一组属于 AFN 以及其他不相关脑网络的 ROI 对,将 4D rs-fMRI 数据集转换为动态功能连接(DFC)矩阵。在这项研究中,我们评估了五种算法的性能,以将来自三个条件(ME、SE、NS)的 DFC 矩阵分类为三个不同类别。使用 K 最近邻(KNN)算法对 ME 条件进行分类,获得了最高的 0.92 准确率。换句话说,应用分类算法使我们能够识别 AFN 的激活,并且 ME 条件是实现这种激活的最佳排列方式。使用模型性能参数确定了对参与者 rs-fMRI 数据分类贡献最大的前 5 个 ROI 对;ROI 对主要位于右侧 AFN 内。这项使用分类算法方法的概念验证研究可以扩展到创建一个参与者级别的近实时反馈系统,以检测跨越多个脑叶的脑网络的激活和调节。
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